An “unprecedented” joint crackdown on software piracy by Chinese police and the US Federal Bureau of Investigation has led to 25 arrests and the seizure of counterfeit software worth $500m, the FBI said on Tuesday.

The investigations into goods pirated from Microsoft and other US companies were hailed by the American software giant as a “milestone in the fight against software piracy”. It said: “Countries around the world are expected to experience a significant decrease in the volume of counterfeit software as a direct result of this action.”